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Flip COB is the most recent trends in LED
manufacturing and packaging. This LED has better thermal performance and allow
higher power than standard SMD package.
COB: Chip on Board
COB is a new technology of LED packaging for LED light engine. Multi LED
chips are packaged together as one lighting module. When it light up, it looks
like a lighting panel.
Figure 1(a) and 1(b) respectively show the
schematic diagrams of a traditional wire-bond COB Chip and no wire-bond flip
COB chip. In Figure 1(a), a traditional COB chip is bonded on the MCPCB
substrate by bonding epoxy and connects to the circuit electrodes via two
bonding wires. The thermal energy generated by the LED chip is dissipated
through the chips’ sapphire substrate, bonding epoxy, followed by a MCPCB
dielectric layer before reaching the metal core. On the other hand, the flip COB
chip shown in Figure 1(b) has the LED chip directly bonded on the circuit
electrodes without the bonding wire and epoxy. The heat generated by the LED is
coupled through the chip bonding pads, circuit electrodes, MCPCB dielectric
layer, and then diffused into the metal core. In comparison, the flip COB chip exhibits less thermal resistance
as its thermal dissipating path excludes the sapphire substrate and bonding
epoxy that are materials having higher thermal resistance.
Thermal decay is a natural characteristic
for LED, as the optical output decreases when the LED junction temperature is
increased. Therefore, the lighting efficacy would decrease following the
increase of the LED junction temperature. In
order to minimize the thermal decay, lowering the thermal resistance becomes
essential to maintain or lower the LED junction temperature while more optical
output is demanded through the increase of driving current.
Because Flip COB chip exhibit less thermal
resistance, it can work under high current, this is important to apply to
automotive led industry. While led bulb has high wattage, it can fit to more
cars and computer won’t show error.
Traditional COB chip connects to the
circuit electrodes via two bonding wires, these bonding wires is possible to
break during package or using. Flip COB chip don’t need these bonding wires,
removing a potential risk and reducing the defective rate.